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How did they come into existence from a photon? Is it really understood how the process works? Is there even a process or is it just something fundamental?

Ray Kay
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  • Please provide more context - are you referring to a specific experiment? It is fairly easy to create electron-positron pairs via laser-matter interaction if the power density is high enough. See http://cuos.engin.umich.edu/researchgroups/hfs/facilities/lambdacubed/ – Peter Diehr Jul 25 '16 at 12:47
  • Have you tried using the internet? eg https://en.wikipedia.org/wiki/Pair_production which is #2 on page 1 when googling your exact title. – sammy gerbil Jul 25 '16 at 12:59
  • Related: http://physics.stackexchange.com/q/166866/50583 – ACuriousMind Jul 25 '16 at 13:07

1 Answers1

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It is understood how the process works. In a nutshell, the energy of a photon is converted to the mass of an electron and positron as is given by Einstein's $E = mc^2$. This is spelled out as follows:

$γ → e^− + e^+$

There are two musts for this:

  1. The photon must have a higher energy than the sum of the rest mass energies of a positron and electron for this to happen ($2 * 0.511 MeV = 1.022 MeV$).
  2. The photon must be near a nucleus in order to satisfy conservation of energy and momentum.

The basic properties, energy transfer, and cross section can be specifically calculated. So, yes, I'd say the mathematics and process are fairly well defined.

More information can be found here.

Hope this helps!

auden
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    Ok, you win :) But I am still not completely convinced, we observe what happens, so we know it's going to happen again but ultimately (personally) I think we will be relying on observations, rather than a underlying theory, for a long time yet. –  Jul 25 '16 at 13:01
  • @count_to_10: I think that we don't understand the why, but we do understand the how (mostly...soon as someone says something to broad/expansive some result is going to come up that makes everyone scratch their heads). I can sort of agree with your comment about observations. What did I win over? – auden Jul 25 '16 at 13:03
  • I thought my comment contradicted your answer and your answer did explain the process properly, so I deleted it. –  Jul 25 '16 at 13:05